Reusable plastic fasteners are commonly used to attach together two panels, yet permit the panels to be detached or disconnected later if desired. For example, in the automotive industry such plastic fasteners are commonly used to attach door trim panels to the supporting sheet metal of the door. Similarly, appliances, such as dishwashers or refrigerators, commonly use such fasteners to also attach trim panels.
The fastener is typically a two piece fastener so that if the panels need to be separated after original installation, such as to service the components in the door, they may be pulled apart so that one portion remains attached to the sheet metal while the other remains attached to the trim panel. The two portions may also desirably be reconnected after separation.
U.S. Pat. No. 4,375,342 to Wollar et al. discloses a reusable plastic fastener including an elongate body portion or pin which mates with a surrounding grommet. The pin includes an enlarged head at one end which rests against the panel or workpiece. The pin is inserted through an opening in the workpiece and into the grommet so that the head remains visible. The grommet includes an enlarged portion defining a flange and a pair of separable legs extending axially outwardly therefrom. The legs are forced apart by insertion of the pin to secure the grommet to the second panel. In addition, the grommet includes lugs on an interior surface thereof. The plunger includes front and rear spaced apart grooves which together with the lugs on the grommet define two detents for the fastener. The two panels are secured together between the enlarged head of the pin and the flange of the grommet.
U.S. Pat. No. 4,393,551 to Wollar et al. discloses a fastener having a head and an integrally formed shank, wherein the head includes a radial slot to permit installation into a first panel by twisting of the fastener. The shank includes a flange and a plurality of barbed-shaped projections to secure the shank within an opening of a second panel.
Another fastener is disclosed in U.S. Pat. No. 4,233,878 to McGauran et al. and includes a shank having a series of circumferential grooves therealong for engaging a grommet which, in turn, includes a nylon sleeve. U.S. Pat. No. 4,122,583 to Grittner et al. discloses another fastener such as for automotive applications that is integrally molded as one piece and includes a rectangular shank and rectangular grommet including outwardly swinging arms to secure to panels together.
U.S. Pat. No. 4,648,766 also to Wollar discloses yet another plastic fastener, such as for removably securing a decorative or trim panel. The fastener includes a shank and an outermost flange with a radial slot as described with reference to U.S. Pat. No. 4,393,551 to permit the head or flange to be rotated into an opening of a first panel. A grommet is integrally molded to the opposite end of the shank so that a frangible web initially connects the grommet to the end of the shank. The grommet includes a flange and a plurality of outwardly extending tabs adjacent the flange to secure the grommet to a second panel. The tabs are secured to the grommet body at two longitudinal positions, and, hence require considerable force to initially seat the grommet in a panel. The grommet is held onto the shank in operation by friction generated by a plurality of circumferential grooves on the shank and a relatively long and smooth bore of the grommet. Unfortunately the force for seating the grommet in the opening in the second panel is relatively high, and the pull-out force needed to later separate the panels is difficult to control. Accordingly, improper seating of the grommet is possible, and damage to one or both of the panels may result from an attempted separation.